The butt welding of tubes to each other is one of those nasty little problems scattered throughout the welding art. The problem is aggravated by the requirement that the delicate weld of axially aligned tubes at their abutting ends requires gas-shielding of the welding process.
The simplistic approach would appear, superficially, one of inserting a rod down the inside of both tubes to hold the tubes in axial alignment while their ends are spot-welded together. Thereafter, the aligning rod could be extracted and the comparatively delicate gas-shielded welding process could be carried out while the tubes are held in position by their spot welds.
The present requirement is to simplify the foregoing procedure by providing a fixture with which the tubes can be clamped in alignment during the gas-shielded welding process. The elimination of tack welds (manually applied) will provide a more uniform weld due to an automatic welding operation. Provision is required for flowing the inert gas through the tubes as they are clamped in alignment by the fixture. Finally, the fixture is required to be readily insertable and removable in the pipes.